Paging examples

1. Paging Examples
Assume a page size of 1K and a 15-bit
logical address space.
How many pages are in the system?

2. • Answer: 2^5 = 32.
• Assuming a 15-bit address space with 8 logical pages.
How large are the pages?

3. • Answer: 2^5 = 32.
• Assuming a 15-bit address space with 8 logical pages.
How large are the pages?
• Answer: 2^12 = 4K. It takes 3 bits to reference 8 logical
pages (2^3 = 8). This leaves 12 bits for the page size
thus pages are 2^12.

4. Consider logical address 1025 and the following
page table for some process P0. Assume a 15-bit
address space with a page size of 1K. What is the
physical address to which logical address 1025
will be mapped?
8
0
2

5. Consider logical address 1025 and the following
page table for some process P0. Assume a 15bit address space with a page size of 1K. What
is the physical address to which logical address
1025 maps?
8
Step 1. Convert to binary:
0
000010000000001
2

6. Consider logical address 1025 and the following
page table for some process P0. Assume a 15bit address space with a page size of 1K. What
is the physical address to which logical address
1025 maps?
8
0
2
Step2. Determine the logical page
number:
Since there are 5-bits allocated to the
logical page, the address is broken up as
follows:
00001
0000000001
Logical page number
offset within
page

7. Consider logical address 1025 and the following
page table for some process P0. What is the
physical address?
00001
0
Step 3. Use logical page
number as an index into
the page table.
2
00001 0000000001
8

8. Consider logical address 1025 and the following
page table for some process P0. What is the
physical address?
00001
8
0
Take the physical page number from
the page table and concatenate the
offset.
The physical address is byte 1.
2
000000000000001